Last year, Potter had a breast cancer scare and chose to work through the fear partially by addressing it on her show. After learning she might have cancer, Potter got in touch with Parenthood creator Jason Katims to share the news.

“I emailed Jason and I said, ‘You know I’m really scared about something. Can we maybe explore this story for Kristina?’ ” Potter recalled. “He emailed me back and he said, ‘Oh, my god. I have the chills. I’m in the writing room. We just broke the story for Kristina.’ ”

Gunn said she worked with Breaking Bad creator Vince Gilligan to flesh out her character, mostly so she would know her motivations.

“We did some talking about her at the beginning, because she wasn’t particularly clear to me,” Gunn said. “So I needed to know about her so I could play her, even if the audience didn’t end up knowing about those things.”

One of the problems? Gunn said it was “confusing” and “bothersome” to her that while her on-screen husband Walter White (Bryan Cranston) was working two jobs, Skyler stayed at home. Gunn didn't understand how Skyler filled her days.

“So we came up with something for her to do at home, which ultimately fell by the wayside. But it justified some things and made it more understandable for me,” she said.

Mara said she’s influenced her character Zoe by suggesting to House of Cards’ creator Beau Willimon that more is less for her character.

“My notes on scripts were always, ‘I think I should say less,’ ” Mara said. “For Zoe in particular, I always felt like she wouldn’t necessarily say that much. Anytime I would go up to Beau while we were shooting or before, he would get his pen out ready to cross out lines.”